Satou kurinosuke has explained with respect to apache
tomcat
servlet generated from a JspOne.jsp page
public final class JspOne_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
Let me explain the general scenario
When you use a jsp page for the first time after it has been deployed in a server it will be translated into
java source code and compiled in to servlet class file by the container and that servlet will implement HttpJspPage.
HttpJspPage interface defines the life cycle method _jspService(HttpServletRequest request, HttpServletResponse response) and extends Servlet interface and JspPage interface in which life cycle methods jspInit() & jspDestroy() are defined. JspPage interface extends Servlet interface which defines init(ServletConfig config) method.